Latex extraction by “bleeding” is possible from the sixth year after crop establishment and proceeds for 25 to 30 years. Stem panel openings are recommended after 50% of the plant population has a minimum stem diameter of 45 cm at 1.5 m high on the tree.
(12) Plant longevity is affected by genotype, climate and crop management. (13) After each “bleeding”, growth stimulators such as ethylene are applied to induce or favor stem cortex recovery and latex production.
(14) Seedling Production Different approaches are available for producing rubber tree seedlings. Initially, it was common to use seeds produced in native areas. However, these materials were lower in quality and negatively affected crop growth and yield.
As a consequence, from 1980 to 1990, an initiative was established to promote high quality seed production in Brazil which increased cultivated rubber tree areas. This initiative also became focused on seedling production to obtain rootstocks and stalks for grafting that further improved crop productivity.
It is well known that high quality seeds are essential to produce vigorous rubber tree seedlings. In addition, the selection and production of clones adapted to different regions and possessing high performance potential contribute to greater crop yields. Rootstocks from seeds of hybrid cultivars are usually more vigorous than those from seeds collected in native areas.
Rubber tree seedling production often involves rootstock growth in nurseries, stalk formation and grafting operations. Production systems to attain these objectives can be accomplished in different ways.
(15) a) Rootstock formation First, seeds are germinated to obtain small seedlings known as “spider paw” that are transferred to the nursery (16) or to plastic bags filled with artificial substrate.
The following photographs (17), (18), (19), and (20) show well-developed seedlings at the proper growth stage to be transferred to the nursery.
(21) b) Clonal gardens There are different clones to establish rubber tree crops. The selection of the most appropriate clone depends on the region and characteristics desired by producers.